The present invention relates to a method of coordinating pressure demands within a brake circuit of an electronically controlled hydraulic brake system for an automotive vehicle. Electronically controlled brake systems include an electronic control unit which applies various algorithms to data collected from a variety of sensors detecting vehicle behavior.
Such algorithms include anti-lock brake control, traction control, electronic stability control (ESC), automatic rollover prevention (ARP), and possibly others. While anti-lock braking controls the brake pressure during a driver-operated braking maneuver, traction control, ESC, and ARP are so-called active brake controls, i.e. a pressure generator, e.g. a pump, will generate brake pressure to be applied to individual wheels independent of the driver's brake activation.
Sometimes two of the algorithms, simultaneously or in overlapping time segments, detect an instability in vehicle behavior, e.g. wheel speeds, yaw rate, lateral acceleration, etc., based on different criteria that would trigger different interventions. Thus an arbitration logic will prioritize one algorithm over the other or find a compromise by initiating a control including components of both algorithms.
In highly dynamic situations, i.e. in situations with rapidly changing pressure demands, a quick intervention and real-time performance is of high importance. In order to provide fluid pressure as quickly as possible during active braking operations, it has been suggested to include high-pressure accumulators which are filled by the pump when currently no intervention is required and connected to the brake lines when necessary. Other suggestions include priming pumps and other additional devices.
Any additional piece of hardware, however, will add to the packaging space, to the weight, and to the price of the brake system.
It is therefore an objective of the present invention to take advantage of existing hardware within the brake system to attain a rapid real-time pressure build-up where needed.